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Peter Anvin" To: Arnd Bergmann , =?ISO-8859-1?Q?Thomas_Wei=DFschuh?= CC: Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Russell King , Catalin Marinas , Will Deacon , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Thomas Bogendoerfer , Vincenzo Frascino , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-mips@vger.kernel.org Subject: Re: [PATCH 1/7] x86/vdso: Respect COMPAT_32BIT_TIME User-Agent: K-9 Mail for Android In-Reply-To: <2b1ac7b9-fcc8-4aa3-a0ad-eb37e4bce030@app.fastmail.com> References: <20260227-vdso-compat_32bit_time-v1-0-3f0286a7bac3@linutronix.de> <20260227-vdso-compat_32bit_time-v1-1-3f0286a7bac3@linutronix.de> <03cd1e21-a2f2-46a1-a674-cbaef9712016@app.fastmail.com> <20260227103226-cc3bb32c-0107-4c09-b81a-ca33ea03ad5c@linutronix.de> <49b7c9f9-198a-49f7-880b-6ae74d7bd985@zytor.com> <2b1ac7b9-fcc8-4aa3-a0ad-eb37e4bce030@app.fastmail.com> Message-ID: <56591FD5-0DD0-4117-BC7B-4565E3F6512E@zytor.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On March 3, 2026 12:50:33 PM PST, Arnd Bergmann wrote: >On Tue, Mar 3, 2026, at 19:11, H=2E Peter Anvin wrote: >> On 2026-02-27 01:34, Thomas Wei=C3=9Fschuh wrote: >>>>> >>>> The thing about gettimeofday() and time() is that they don't have >>>> a 64-bit version and libc implementations are expected to call >>>> clock_gettime() instead=2E The result was that there was never a >>>> patch to turn the off either=2E >>>=20 >>> gettimeofday() is currently the only way to get the timezone of the ke= rnel=2E >>> But I guess this is a legacy thing anyways=2E If you say we should dro= p it, >>> let's drop it=2E >>>=20 >> >> The time zone in the kernel has never worked anyway, as it would requir= e the >> kernel to contain at least the forward portion of the zoneinfo/tzdata t= able in >> order to actually work correctly=2E The only plausible use of it would = be for >> local time-based filesystems like FAT, but I don't think we bother=2E >> >> A bigger question is whether or not we should omit these from the vDSO >> completely (potentially causing link failures) or replace them with stu= bs >> returning -ENOSYS=2E > >I see no harm in keeping gettimeofday() in the vdso when >COMPAT_32BIT_TIME is turned on, as existing code will call it >no matter whether it's in the vdso or the syscall=2E > >Equally, I see no point in having either version of >gettimeofday() or settimeofday() when COMPAT_32BIT_TIME is >disabled, as clearly anything calling it would pass incorrect >data for times past 2038=2E > >Neither glibc nor musl support actually returning the kernel >timezone to callers of gettimeofday in modern versions that >support time64 syscalls=2E > > Arnd > That wasn't the point=2E The point was what kind of error behavior we want= =2E